Three years have passed since a catastrophic event decimated the monster population, leaving only three survivors who have since evolved into far deadlier versions of themselves. As 1999 dawns, an extraterrestrial creature of immense power arrives on Earth alongside an army of subordinates, intent on subjugating the planet and establishing dominion over all life. The last remaining monsters must set aside their rivalries and confront this otherworldly threat to prevent total conquest, while simultaneously battling for supremacy among themselves in a bid to reclaim the title of King of the Monsters.